CDK4 and glioblastoma: Previous studies proved the CDK4/6 pathway as being active in solid tumours, such as liposarcoma, rhabdomyosarcoma, non-small-cell lung cancer, glioblastoma, oesophageal cancer, melanoma and breast cancer.9 The role of the most prominent CDK4/6 inhibitors palbociclib (Ibrance), ribociclib (Kisqali) and abemaciclib (Verzenio) in monotherapy and combined therapy is under evaluation in several phase 1, 2 or 3 studies.